Glass package that is hermetically sealed with a frit and method of fabrication

ABSTRACT

A hermetically sealed glass package and method for manufacturing the hermetically sealed glass package are described herein using an OLED display as an example. Basically, the hermetically sealed OLED display is manufactured by providing a first substrate plate and a second substrate plate and depositing a frit onto the second substrate plate. OLEDs are deposited on the first substrate plate. An irradiation source (e.g., laser, infrared light) is then used to heat the frit which melts and forms a hermetic seal that connects the first substrate plate to the second substrate plate and also protects the OLEDs. The frit is glass that was doped with at least one transition metal and possibly a CTE lowering filler such that when the irradiation source heats the frit, it softens and forms a bond. This enables the frit to melt and form the hermetic seal while avoiding thermal damage to the OLEDs.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation-in-part application of U.S. patentapplication Ser. No. 10/414,794, filed Apr. 16, 2003.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to hermetically sealed glass packages thatare suitable to protect thin film devices that are sensitive to theambient environment. Some examples of such devices are organic emittinglight diode (OLED) displays, sensors, and other optical devices. Thepresent invention is demonstrated using OLED displays as an example.

2. Description of Related Art

OLEDs have been the subject of a considerable amount of research inrecent years because of their use and potential use in a wide variety ofelectroluminescent devices. For instance, a single OLED can be used in adiscrete light emitting device or an array of OLEDs can be used inlighting applications or flat-panel display applications (e.g., OLEDdisplays). The traditional OLED displays are known as being very brightand having a good color contrast and wide viewing angle. However, thetraditional OLED displays and in particular the electrodes and organiclayers located therein are susceptible to degradation resulting frominteraction with oxygen and moisture leaking into the OLED display fromthe ambient environment. It is well known that the life of the OLEDdisplay can be significantly increased if the electrodes and organiclayers within the OLED display are hermetically sealed from the ambientenvironment. Unfortunately, in the past it was very difficult to developa sealing process to hermetically seal the OLED display. Some of thefactors that made it difficult to properly seal the OLED display arebriefly mentioned below:

-   -   The hermetic seal should provide a barrier for oxygen (10⁻³        cc/m²/day) and water (10⁻⁶ g/m²/day).    -   The size of the hermetic seal should be minimal (e.g., <2 mm) so        it does not have an adverse effect on size of the OLED display.    -   The temperature generated during the sealing process should not        damage the materials (e.g., electrodes and organic layers)        within the OLED display. For instance, the first pixels of OLEDs        which are located about 1-2 mm from the seal in the OLED display        should not be heated to more than 100° C. during the sealing        process.    -   The gases released during sealing process should not contaminate        the materials within the OLED display.    -   The hermetic seal should enable electrical connections (e.g.,        thin-film chromium) to enter the OLED display.

Today the most common way for sealing the OLED display is to usedifferent types of epoxies, inorganic materials and/or organic materialsthat form the seal after they are cured by ultra-violet light. Vitexsystems manufactures and sells a coating under the brand name of Batrix™which is a composite based approach where alternate layers of inorganicmaterials and organic materials can be used to seal the OLED display.Although these types of seals usually provide good mechanical strength,they can be very expensive and there are many instances in which theyhave failed to prevent the diffusion of oxygen and moisture into theOLED display. Another common way for sealing the OLED display is toutilize metal welding or soldering, however, the resulting seal is notdurable in a wide range of temperatures because of the substantialdifferences between the coefficients of thermal expansions (CTEs) of theglass plates and metal in the OLED display. Accordingly, there is a needto address the aforementioned problems and other shortcomings associatedwith the traditional seals and the traditional ways for sealing the OLEDdisplays. These needs and other needs are satisfied by the hermeticsealing technology of the present invention.

BRIEF DESCRIPTION OF THE INVENTION

The present invention includes a hermetically sealed OLED display andmethod for manufacturing the hermetically sealed OLED display.Basically, the hermetically sealed OLED display is manufactured byproviding a first substrate plate and a second substrate plate anddepositing a frit onto the second substrate plate. OLEDs are depositedon the first substrate plate. An irradiation source (e.g., laser,infrared light) is then used to heat the frit which melts and forms ahermetic seal that connects the first substrate plate to the secondsubstrate plate and also protects the OLEDs. The frit is glass that wasdoped with at least one transition metal and possibly a CTE loweringfiller such that when the irradiation source heats the frit, it softensand forms a bond. This enables the frit to melt and form the hermeticseal while avoiding thermal damage to the OLEDs.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete understanding of the present invention may be obtainedby reference to the following detailed description when taken inconjunction with the accompanying drawings wherein:

FIGS. 1A and 1B are a top view and a cross-sectional side viewillustrating the basic components of a hermetically sealed OLED displayin accordance with the present invention;

FIG. 2 is a flowchart illustrating the steps of a preferred method formanufacturing the hermetically sealed OLED display shown in FIGS. 1A and1B;

FIG. 3A is a perspective view illustrating two substrate plates thatwere hermetically sealed by a laser in experiment #1;

FIG. 3B-3F are absorption spectra of exemplary glasses that were dopedwith different transition metals;

FIG. 3G is a photograph of a top view of two glass plates having a sealformed from an iron vanadium phosphate glass frit that was melted by alaser which had a translation speed that varied from 0.2 mm/s to 5 mm/sfrom the left to the right in experiment #1;

FIG. 3H is a photograph of a top view of two glass plates having a sealformed from a titanium vanadium phosphate glass frit that was melted bya laser which had a translation speed that varied from 0.2 mm/s to 5mm/s from the left to the right in experiment #1;

FIGS. 4A and 4B are graphs of transmission curves of an exemplaryvanadate iron phosphate glass frit (FIG. 4A) and Corning Code 1737 glasssubstrate plates (FIG. 4B) used in experiment #2;

FIG. 4C is a photograph of a side view of crack-free sealed glass platesmade in experiment #2;

FIG. 5A is a diagram illustrating a laser and a split-beam opticarrangement used to heat two sides of the glass plates in experiment #3;

FIG. 5B is a top view of a preform frit that was placed a small distanceaway from the free edges of a glass substrate plate in experiment #3;

FIG. 5C is a photograph of crack-free sealed glass plates made inexperiment #3;

FIG. 6A shows a graph of the temperature measured as a function of timewhen an infrared lamp was used to seal of each of the four sides of a1″×1″ assembly of Code 1737 glass plates using a 5801 blend fritdescribed in experiment #4;

FIG. 6B shows a SEM cross-section photograph of a 1″×1″ assembly of Code1737 glass plates sealed with a 5817 blend frit which was heated by aninfrared lamp as described in experiment #4;

FIG. 6C is a photograph of a crack-free assembly of Code 1737 glassplates that were sealed with a 5913 blend frit which was heated by alaser as described in experiment #4;

FIG. 7A is a graph of a near-infrared transmittance curve for atitano-vandadium phosphate glass frit (20TiO₂—P₂O₅-50V₂O₅, molar basis)described in experiment #5; and

FIG. 7B is a graph that shows expansion mismatch data measured as afunction of temperature for a butt-seal where a 5895 blend frit wasapplied to one Code 1737 glass plate in experiment #5.

DETAILED DESCRIPTION OF THE DRAWINGS

Referring to FIGS. 1-7, there are disclosed in accordance with thepresent invention a hermetically sealed OLED display 100 and method 200for manufacturing the OLED display 100. Although the sealing process ofthe present invention is described below with respect to the fabricationof a hermetically sealed OLED display 100, it should be understood thatthe same or similar sealing process can be used in other applicationswhere two glass plates need to be sealed to one another. Accordingly,the present invention should not be construed in a limited manner.

Referring to FIGS. 1A and 1B there are a top view and a cross-sectionalside view illustrating the basic components of the hermetically sealedOLED display 100. The OLED display 100 includes a multilayer sandwich ofa first substrate plate 102 (e.g., glass plate 102), an array of OLEDs104, a doped frit 106 (e.g., see experiments #'s 1-5 and TABLES 2-5) anda second substrate plate 107. The OLED display 100 has a hermetic seal108 formed from the frit 106 which protects the OLEDs 104 locatedbetween the first substrate plate 102 and the second substrate plate 107(e.g., glass plate 107). The hermetic seal 108 is typically locatedaround the perimeter of the OLED display. 100. And, the OLEDs 104 arelocated within a perimeter of the hermetic seal 108. How the hermeticseal 108 is formed from the frit 106 and the ancillary components suchas the irradiation source 110 (e.g., laser 110 a and infrared lamp 110b) which are used to form the hermetic seal 108 are described in greaterdetail below with respect to FIGS. 2-7.

Referring to FIG. 2, there is a flowchart illustrating the steps of thepreferred method 200 for manufacturing the hermetically sealed OLEDdisplay 100. Beginning at steps 202 and 204, the first substrate plate102 and the second substrate plate 107 are provided so that one can makethe OLED display 100. In the preferred embodiment, the first and secondsubstrate plates 102 and 107 are transparent glass plates like the onesmanufactured and sold by Corning Incorporated under the brand names ofCode 1737 glass or Eagle 2000™ glass. Alternatively, the first andsecond substrate plates 102 and 107 can be transparent glass plates likethe ones manufactured and sold by the companies like Asahi Glass Co.(e.g., OA10 glass and OA21 glass), Nippon Electric Glass Co., NHTechnoand Samsung Corning Precision Glass Co. (for example).

At step 206, the OLEDs 104 and other circuitry are deposited onto thefirst substrate plate 102. The typical OLED 104 includes an anodeelectrode, one or more organic layers and a cathode electrode. However,it should be readily appreciated by those skilled in the art that anyknown OLED 104 or future OLED 104 can be used in the OLED display 100.Again, it should be appreciated that this step can be skipped if an OLEDdisplay 100 is not being made but instead a glass package is being madeusing the sealing process of the present invention.

At step 208, the frit 106 is deposited along the edges of the secondsubstrate plate 107. For instance, the frit 106 can be placedapproximately 1 mm away from the free edges of the second substrateplate 107. In the preferred embodiment, the frit 106 is a lowtemperature glass frit that contains one or more absorbing ions chosenfrom the group including iron, copper, vanadium, and neodymium (forexample). The frit 106 may also be doped with a filler (e.g., inversionfiller, additive filler) which lowers the coefficient of thermalexpansion of the frit 106 so that it matches or substantially matchesthe coefficient of thermal expansions of the two substrate plates 102and 107. The compositions of several exemplary frits 106 are providedbelow with respect to experiment #'s 1-5 and TABLES 2-5.

At step 210 (optional), the frit 106 can be pre-sintered to the secondsubstrate plate 107. To accomplish this, the frit 106 which wasdeposited at step 208 onto the second substrate plate 107 is then heatedso that it becomes attached to the second substrate plate 107. A moredetailed discussion about the optional step 210 is provided below withrespect to experiment #3.

At step 212, the frit 106 is heated by the irradiation source 110 (e.g.,laser 110 a, infrared lamp 110 b) in a manner so that the frit 106 formsthe hermetic seal 108 which connects and bonds the first substrate plate102 to second substrate plate 107 (see FIG. 1B). The hermetic seal 108also protects the OLEDs 104 by preventing oxygen and moisture in theambient environment from entering into the OLED display 100. As shown inFIGS. 1A and 1B, the hermetic seal 108 is typically located just insidethe outer edges of the OLED display 100. The frit 106 can be heatedusing anyone of a number of irradiation sources 110 such as a laser 110a (see experiment #'s 1-3) and an infrared lamp 110 b (see experiment #4).

Described below are several experiments that were conducted by one ormore of the inventors. Basically, the inventors have experimented withand used different types of irradiation sources 110 to heat differenttypes of frits 106 in order to connect and bond together two Code 1737glass plates 102 and 107. The different compositions of these exemplaryfrits 106 are provided below with respect to experiment #'s 1-5.

Experiment #1

In this experiment, the irradiation source 110 was a laser 110 a (e.g.,810 nm Ti:sapphire laser 110 a) that emitted a laser beam 112 a througha lens 114 a and through the first substrate plate 102 which heated andsoftened the frit 106 (see FIG. 3A). In particular, the laser beam 112 awas moved such that it effectively heated and softened the frit 106which caused the frit 106 to form the hermetic seal 108 that connectedthe first substrate plate 102 to the second substrate plate 107. Thelaser 110 a emitted a laser beam 112 a with a specific wavelength (e.g.,800 nm wavelength) and the frit 106 was made from glass doped with oneor more transition metals (e.g., vanadium, iron, and/or neodymium) so asto enhance its absorption property at the specific wavelength of thelaser beam 112 a. This enhancement of the absorption property of thefrit 106 means that when the emitted laser beam 112 a was absorbed bythe frit 106, the frit softened and formed the hermetic seal 108. Incontrast, the substrate glass plates 102 and 107 (e.g., Code 1737 glassplates 102 and 107) were chosen such that they did not absorbirradiation from the laser 110 a. Thus, the substrate plates 102 and 107had relatively low absorption at the specific wavelength of the laserbeam 112 a which helped to minimize the undesirable transfer of heatfrom the forming hermetic seal 108 to the OLEDs 104. Again, the OLEDs104 should not be heated to more than 80-100° C. during the operation ofthe laser 110 a. It should be noted that the OLEDs 104 were not locatedon the substrate plates in this experiment.

As mentioned above, to increase the absorption of the frit 106 it wasnecessary to dope the glass with one or more transition metals such asvanadium, iron, or neodymium (for example). This was done because theaforementioned transition metals have a large absorption cross-sectionaround 800-nm as illustrated by the absorption spectrum graphs in FIGS.3B-3F. It should be understood that the choice of the transitionmetal(s) is tied to the particular type laser 110 a and with the powerof the laser 110 a and the translation speed of the laser 110 a. Forinstance, an 810-nm, 30-watt semiconductor laser with fiber delivery oflight may be a good choice based on price, reliability, and maintenancecost.

To demonstrate the feasibility of this approach two exemplary frits 106were laser-heated using a 0.9 watt, 800 nm Ti:sapphire laser 110 a theoutput of which was focused into the frit 106 by a 10 cm lens 114 a. Theexemplary frits 106 were placed between two 1-mm thick Code 1737 glassplates 102 and 107. The first frit 106 was made from glass containingwith iron, vanadium and phosphorus. FIG. 3G is a photograph of the seal108 formed from this frit 106 that was softened by laser 111 a which hada translation speed that varied from 0.2 mm/s to 5 mm/s from the left tothe right. And, the second frit 106 was made from glass containing withtitanium, vanadium and phosphorous. FIG. 3H is a photograph of the seal108 formed from this frit 106 that was melted by laser 111 a which had atranslation speed that varied from 0.2 mm/s to mm/s from the left to theright. During the formation of these seals 108, no sensible rise in thetemperature was observed in the glass plates 102 and 107. And, nocracking was observed in the glass plates 102 and 107.

It should be readily appreciated that depending on the opticalproperties of the particular frit 106 and substrate plates 102 and 107other types of lasers 110 a can be used which operate at differentpowers, different speeds and different wavelengths. However, the laserwavelength should be within the band of high absorption in theparticular frit 106. For instance, Ytterbium (900 nm<λ<1200 nm), Nd:YAG(λ=1064 nm), Nd:YALO (λ=1.08 μm), and erbium (λ≈1.5 μm) CW lasers can beused.

Experiment #2

In this experiment, a CO₂ laser 110 a was used to locally heat a frit106 dispersed along the edges of the substrates plates 102 and 107without causing a significant temperature rise away from the sealededges. First, a thin layer of V₂O₅—Fe₂O₃—P₂O₅ preform frit 106containing fillers to enable a CTE match to display glass was spreadalong the edge of one of the Code 1737 glass plates 102 and 107 (seeFIG. 3A). Then the CO₂ laser 110 a heated the vanadate iron phosphateglass frit 106. At the softening temperature of the frit 106, thevanadate iron phosphate glass frit 106 flowed to bond together the Code1737 glass plates 102 and 107 and then solidified during a subsequentcooling cycle to form a hermetic seal 108. FIGS. 4A and 4B are graphs oftransmission curves of the vanadate iron phosphate glass frit 106 andthe Code 1737 glass substrate plates 102 and 107.

Another aspect of this experiment related to the placement of thepreform vanadate iron phosphate glass frit 106 in between the Code 1737glass substrate plates 102 and 107. Since flaws can be easily introducedalong the edges of the Code 1737 glass plates 102 and 107 from priorprocessing steps such as cutting and handling, the probability of edgecracking at the interface of the frit 106 and plates 102 and 107 isincreased for a given temperature gradient and CTE mismatch when theinitial flaw size is greater. And, since the thermal stresses inducedduring lasing and subsequent cooling cycles are elastic in nature thereis no relaxation of stresses. To address this concern, the preformvanadate iron phosphate glass frit 106 in this experiment was applied ata small distance away from the free edges of glass substrates 102 and107 (see FIGS. 3A and 4C).

Experiment #3

In this experiment, the irradiation source 110 was a laser 110 a (e.g.,CO₂ laser 110 a) that emitted a laser beam 112 a through a split-beamoptics arrangement 500 which split the laser beam 112 a into two laserbeams 112 a′ and 112 a′ which where then directed towards the first andsecond Code 1737 glass plates 102 and 107 (see FIG. 5A). As shown, thelaser 110 a emits the laser beam 112 a towards the split-beam opticsarrangement 500 which includes a 50/50 beam splitter 502 that splits thelaser beam 112 a into two laser beams 112 a′ and 112 a″. The first laserbeam 112 a′ is reflected off a mirror 504 (e.g., Au coated mirror 504)so that it is directed through a lens 506 onto the first Code 1737 glassplate 102. And, the second laser beam 112 a′ is reflected off a seriesof mirrors 508 and 510 (e.g., Au coated mirrors 508 and 510) so that itis directed through a lens 512 onto the second Code 1737 glass plate107. The use of the split-beam optics arrangement 500 to deliver theheat to a localized area on the substrate plates 102 and 107, enabledthe inventors to soften and bond an exemplary frit 106 (described below)in a manner where the temperature distribution and residual stresses aremanageable to achieve a reliable sealed assembly. It should be notedthat the split-beam optics arrangement 500 could have been used inexperiment #'s 1 and 2 and that there are many different types ofarrangements which could be used in the present invention to split alaser beam 112 a so that it interfaces with both substrate plates 102and 107.

In this experiment, an exemplary V₂O₅—ZnO—P₂O₅ (VZP) frit 106 and Code1737 glass substrate plates 102 and 107 were chosen. The first step 210of sealing, i.e. pre-sintering the VZP frit 106 to plate 107 wasperformed at 400° C. in furnace environment for 1 hour, and followed byfurnace cooling to prevent cracking. Good wettability, and hencebonding, was observed at the interface of the VZP frit 106 and plate 107without any indication of local delamination or non-adhered region.Then, the second step 212 of sealing followed by using a localized CO₂laser 110 a. In particular, the edges of both surfaces of the substrateplates 102 and 107 were heated locally to the softening temperature ofthe VZP frit 106 by the CO₂ laser 110 a. The CO₂ laser 110 a emitted asingle beam 112 a which was split into two beams 112 a′ and 112 a′ thatwere focused onto the substrate plates 102 and 107 (see FIG. 5A). And,FIG. 5C shows a photo of a top view of the bonded substrate plates 102and 107.

Experiment #4

In this experiment, the irradiation source 110 was a 1000 watt infraredlamp 110 b that was controlled by a variable voltage controller. Thisparticular infrared lamp emitted a light over a wavelength range ofapproximately 800 to 2000 nm. The samples that were sealed using theinfrared lamp 110 b consisted of two 1″×1″ Code 1737 glass plates 102and 107, where an exemplary frit 106 was applied as a thin strip alongthe 4 edges of one of the plates 102 and 107. The compositions of someexemplary frits 106 used in experiment #4 are provided in TABLE #1.TABLE 1* Blend Blend make-up (wt.%) Composition (mole %) # Glass fritFiller Glass Frit Filler 5801 (80%) (20%) (mean TiO₂ 20 Li₂O 25 (meanparticle particle size = P₂O₅ 30 Al₂O₃ 25 size = 15-20 15-20 μm) V₂O₅ 50SiO₂ 50 5817 (70%) (30%) (mean Fe₂O₃ 12.5 Li₂O 25 (mean particleparticle size = P₂O₅ 35 Al₂O₃ 25 size = 15-20 15-20 μm) V₂O₅ 52.5 SiO₂50 5913 (80%) (20%) (mean ZnO 20 Li₂O 25 (mean particle particle size =P₂O₅ 30 Al₂O₃ 25 size = 5-10 μm) 5-10 μm) V₂O₅ 50 SiO₂ 50*It should be understood that these frits 106 could have been used inany of the other experiments described herein to seal Code 1737 glassplates 102 and 107.

As mentioned earlier, it is important when infrared radiation is used toseal a frit 106 that the frit 106 absorbs heat in the infrared region.As described above, vanadium is a particularly strong infrared absorberin oxide glasses. As such, most of the initial calibration and sealingwork in this experiment was done using frits 106 having blend 5801,which consisted of a mixture of a titano-vanadium frit and lithiumalumino-silicate filler (see TABLE #1). The 5801 blend powder was firstmade into a paste using a suitable solvent/binder system such as amylacetate/nitrocellulose, or pine oil, loaded into a syringe, and thenhand-dispensed along the edges of one of the Code 1737 glass plates 102or 107. After applying the 5801 blend frit 106, the two glass plates 102and 107 were manually pressed over each other using mild hand pressure,and then placed in an oven at 100° C. to dry the 5801 blend frit 106.

The sample plates 102 and 107 were then placed about 40 mm under theinfrared lamp (the approximate focal length of the lamp) and set on topof a piece of refractory cloth to serve as insulation. The sealing step212 was carried out a single edge at a time. A refractory block made ofalumina was placed over the entire surface area of the glass plates 102and 107 to serve as an infrared mask with the exception of the actualseal edge that was to be sealed. The temperature in the sample glassplates 102 and 107 was monitored by a thermocouple placed in the centerof the two plates 102 and 107 through a small hole drilled through thetop plate 102. Once the masked glass plates 102 and 107 and thermocouplewere placed under the IR lamp, the lamp controller was turned to 10% ofmaximum power, and the sample plates 102 and 107 were then oriented foractual sealing. The lamp controller was then turned off, final checkswere made of the thermocouple, and then the power was turned immediatelyto the level used for sealing (typically 40-60% of maximum output).

During the operation of the infrared lamp, the seal edge was viewed withinfrared-absorbing protective glasses. Once softening was observed inthe 5801 blend frit 106, the power was immediately turned-off to theinfrared lamp, and the lamp itself was moved away from the sample plates102 and 107. The typical time to seal one edge was approximately 60seconds. FIG. 6A shows a graph of the temperature measured as a functionof time during the sealing of each of the 4 sides of a 1″×1″ assembly ofCode 1737 glass plates 102 and 107 using the 5801 blend frit 106. Itshould be noted that the maximum center temperature ranged fromapproximately 75° to 95°. FIG. 6B shows a SEM cross-section of the 1″×1″pieces of Code 1737 glass plates 102 and 107 sealed in the same mannerabove but the 5817 blend frit 106 was used instead of the 5801 blendfrit 106. The micrograph shows the filler particles dispersed in thewell-melted 5817 blend frit 106. As can be seen, the 5817 blend frit 106does contain a few large blisters or voids, possibly caused by entrappedbinders. It should be noted that despite the short-heating time (60seconds), the 5817 blend frit 106 is both well melted and exhibits goodadhesion to the Code 1737 glass plates 102 and 107.

In addition to the aforementioned 5801 and 5817 blend frits 106,infrared-sealing work was also carried out with the 5913 blend.Approximately half of the sealed sample plates 102 and 107 were testedand the seal was determined to be hermetic-using the criterion of notexhibiting any leak larger than 10⁻⁸ cm³/s in a He leak test.

It should be noted that a laser 110 a has also been used to melt one ofthe frits 106 listed in TABLE #1. In particular, a 7 watt, 810-nm,continuous wave (CW) semiconductor laser 110 a emitting a laser beam 112a focused onto a 2.5 mm spot and moved at a velocity of 0.5 mm/s wasused to melt 5913 blend frit 106 (see FIG. 6C). Before the operation ofthe laser 110 a, the 5913 blend frit 106 was screen-printed, pre-fired,and ground to reduce its thickness variation to less than 5-10 μm.

Experiment #5

Before discussing the details of this experiment, one should rememberthat there are several considerations which should be kept in mind whendesigning a frit 106 that can be used to make a hermetically sealed OLEDdisplay 100. Following is a list of some of these considerations:

-   -   Sealing temperature—To avoid thermal degradation of the OLEDs        104, the frit 106 should seal at a low enough temperature such        that the temperature experienced a short distance (1-3 mm) from        the sealed edge in the OLED display 100 should not exceed        approximately 100° C.    -   Expansion compatibility—The frit 106 should be expansion matched        with substrate plates 102 and 107 to limit sealing stresses and        thereby eliminate hermeticity loss by fractures in the seal.    -   Hermeticity—The frit 106 should form a hermetic seal and provide        long-term protection for the constituents in the OLED display        100.

The requirement that frit-sealing be accompanied by at best only aminimal temperature rise in the adjacent OLEDs can be satisfied with alow temperature sealing frit 106. However, most low temperature oxidefrits of reasonable durability have CTE values well above the CTEs ofthe substrates plates 102 and 107. As such, the high CTE of lowtemperature glass frits may require the use of filler additions, orinert phases that lower the CTE. These fillers may be “additive fillers”such as lithium alumino-silicate crystalline phases which have anintrinsically-lower CTE themselves, or “inversion fillers” such as Co—Mgpyrophosphate which introduce dimensional change through a phasetransformation during heating or cooling. Accordingly, to meet the OLEDsealing temperature requirements, a low temperature filled frit 106 incombination with some form of localized edge heating such as an infraredlamp 110 b or CO₂ laser 110 a may be required to minimize the adjacenttemperature rise during sealing.

Several potential low melting frits 106 suitable for sealing OLEDdisplays 100 made from Code 1737 glass plates 102 and 107 are listed inTABLE #2. These potential frits 106 were selected on the basis of a lowT_(g) (i.e., <350° C.), and a low furnace sealing temperature (<550°C.). Although these frits 106 were all prepared by normal glass-meltingtechniques, it should be noted that many of these frits 106 may also beprepared by sol-gel techniques. The compositions listed in TABLE 2include the following frits 106:

-   -   Sn—Zn phosphates (SZP)—These frits 106 have moderate CTE values        (100-110×10⁻⁷/° C.), good aqueous durabilities, but are troubled        by a tendency for weak adhesion. As such, they may require an        inversion filler to lower the CTE, and an infrared absorber        (e.g., transition metal(s)) to permit heating by localized        devices such as the semi-conductor 110 a and the infrared lamp        110 b.

Mixed alkali zinc phosphates (RZP)—These frits 106 have high values ofCTE (130×10⁻⁷/° C.), but demonstrate good adhesion. As such, they mayrequire relatively large additions of fillers to lower the CTE to thedesired 37×10⁻⁷/° C. range. As a result, sealing temperatures are high.

-   -   Vanadium-phosphate glasses—These frits 106 combine the unique        features of low T_(g) and low CTE. They exhibit good adhesion,        but suffer from the potential drawback of poor aqueous        durability. Since vanadium itself is a strong infrared absorber        in silicate glasses, these glasses are attractive for many        localized sealing techniques.

Pb-borate glasses—These frits 106 are based on the PbO—B₂O₃ eutecticwhich is derived from tv sealing frit compositions. Their high expansioncoefficients may require appreciable amounts of filler addition to lowertheir CTE to match that of the potential display glasses.

Mixed compositions (such as zinc mixed alkali phosphate with PbO andV₂O₅)— Mixed frits 106 typically offer advantages over the individualend-members by possessing attributes such as good IR absorption, butgenerally have disadvantages such as high CTE. TABLE 2* RZP + V, PbO RZPMixed SZP Mixed V-phos alkali-Zn- Sn-Zn- alkali-Zn- Vanadium PBphosphate + Description phosphate phosphate phosphate Pb-borate V. andPb Typical 60% SnO 45% ZnO 50% V₂O₅ 62% PbO 30% P₂O₅ composition 32%P2O₅ 33% P₂O₅ 30% P₂O₅ 34% B₂O₃ 23% ZnO (mole %)  6% ZnO 20% R₂O 20% ZnO 3% SiO₂ 20% R₂O  2% B₂O₃  2% Al₂O₃  1% Al₂O₃ 15% PbO 10% V₂O₅  2% Al₂O₃Typical 300° 325° 300° 350° 310° T_(g) (° C.) Furnace 475-500° 500-550°425-450° 500-550° 500-550° sealing temperature for 37 CTE glass (° C.)Typical CTE 110 130 70 130 140 (10⁻⁷/° C.) Positive Low T₉, Good Low T₉,low Good Good features good adhesion CTE, good adhesion adhesiondurability adhesion Negative May May require May require May require Mayrequire features require inversion additive inversion inversioninversion filler + IR filler. filler + IR filler; filler + absorber;absorber; high IR high furnace high furnace furnace absorber, sealingsealing sealing adhesion temp. temp. temp. weak*It should be understood that these frits 106 could have been used inany of the other experiments described herein to seal Code 1737 glassplates 102 and 107.

As noted in TABLE #2, vanadium-phosphate based glass frits 106 offer aunique combination of low T_(g), and low CTE. Vanadium is a stronginfrared absorber in silicate glasses thus it is a strong candidate inlocalized sealing methods such as IR lamp, and both near-, and farinfrared lasers (i.e., semiconductor lasers at 800-900 nm, and CO₂ laserat 10.6 μm). The starting point for the vanadium phosphate work wasseveral low Tg glasses in the Fe₂O₃—P₂O₅—V₂O₅ and TiO₂—P₂O₅—V₂O₅systems. FIG. 7A shows a near-infrared transmittance curve for atitano-vandadium phosphate glass frit, 895AFD (20TiO₂—P₂O₅-50V₂O₅, molarbasis) (the 895 AFD frit is not shown in TABLE #2). Please note theabsorption of this frit 106 in the 800-1500 nm wavelength range. Incontrast, please note that the Code 1737 glass plates 102 and 107 arenearly completely transparent in the 800-1500 nm wavelength range.

Although the 895 AFD vanadium phosphate glass frits 106 has a low CTE,its CTE may not be low enough to match the CTE of the Code 1737 glassplates 102 and 107 without the addition of fillers. Since, the frit 106has a relatively-low CTE this permits the use of “additive” fillers tolower the CTE, rather than “inversion” fillers which can producemicrocracking, resulting in non-hermetic seals. Unfortunately, the 895AFD frit 106 even with filler levels close to the maximum amount (≈25-30wt. %) still did not exhibit a satisfactory expansion match to Code 1737glass plates 102 and 107.

However, continued composition research resulted in the discovery thatzinc vanadium phosphate glass frits 106 can be made which haveexpansions low enough to permit a close CTE match to Code 1737 glassplates 102 and 107 when fillers are added. Measured values of Tg and CTEfor one of these frits which has a composition 20ZnO-30P₂O₅-50V₂O₅(molar basis) were, respectively, 300° C., and 70×10⁻⁷/° C. In fact,5895 blend frit 106 described below but not listed in TABLE #2 has acombination of zinc vanadium phosphate and additive fillers which hasshown excellent expansion compatibility and good bonding with Code 1737glass plates 102 and 107. The 5895 blend frit 106 is composed of Znvanadium phosphate frit (molar basis: 20ZnO-30P₂O₅-50V₂O₅) andβ-eucryptite glass-ceramic (molar basis: 25Li₂O-25Al₂O₃-50SiO₂) asfollows (wt. Basis):

-   -   frit, (5-10 μm mean particle size) 75%    -   filler (5-10 μm mean particle size) 10%    -   filler (15-20 μm mean particle size) 15%        FIG. 7B is a graph that shows expansion mismatch data measured        as a function of temperature for a butt seal where a blend 5895        frit 106 was applied to one Code 1737 glass plate 102. The seal        was prepared from a paste using amyl acetate and nitrocellulose        as the vehicle/binder system, and then fired in a furnace with a        viewing port for a polarimeter. It was heated to 450°, held one        hour, and then cooled to room temperature. During the cooling        cycle, photoelastic measurements were made at specific        temperature intervals to monitor the retardation in the Code        1737 glass plate 102 that was caused by the expansion mismatch        with the frit 106. The photoelastic measurements were used to        calculate the total expansion mismatch, δ_(T) between the        substrate glass 102 and frit 106 as shown in EQUATION #1:        δ_(T) =ΔT(α_(g)−α_(f))  (1)        where: α_(g), α_(f)=expansion coefficients of glass, and frit,        respectively; and ΔT=temperature range of interest

It should be noted that the maximum expansion mismatch shown in FIG. 7Bbetween the 5895 blend frit 106 and Code 1737 glass plate 102 and 107was approximately +350 ppm at 125° C., and the room temperature mismatchwas +125 ppm, with the frit 106 in mild tension in both instances. Thesemismatch values indicate relatively good expansion compatibility betweenthe blend 5895 frit 106 and Code 1737 glass substrate 102 and 107. Aninverse sandwich seal of 5895 blend frit 106 and Code 1737 glass platefurnace-fired at 450° C. for 1 hour showed a mismatch of −25 ppm (fritin mild compression), indicating the good expansion compatibilitybetween the 5895 blend frit 106 and Code 1737 glass plate 107.

These zinc vanadium phosphate frits 106 also offer promise for meetingthe hermeticity requirements for OLED sealing. Several 1″×1″ assembliesof Code 1737 glass plates heated either by infrared lamp 110 b or 810 nmlaser 110 a and sealed with the 5895 blend frit 106 passed the He-leaktest by holding vacuum down to the lowest leak rate measured by theequipment, 1×10⁻⁸ cm³/s. In addition, separate temperature measurementsby an infrared camera, thermocouple, and thermal indicator paint madeduring 810 nm laser frit sealing all indicated a maximum temperature≦100° C. at 1 mm from the seal edge.

Yet another potential low melting vanadium frit 106 suitable for sealingOLED displays 100 made from Code 1737 glass plates 102 and 107 is listedin TABLES 3-5. TABLE 3 identifies this inventive vanadium frit 106,where all of the elements are specified in mole %: TABLE 3 vanadium frit106 K₂O  0-10 Fe₂O₃  0-20 Sb₂O₃  0-20 ZnO  0-20 P₂O₅ 20-40 V₂O₅ 30-60TiO₂  0-20 Al₂O₃ 0-5 B₂O₃ 0-5 WO₃ 0-5 Bi₂O₃ 0-5

TABLE 4 list a preferred composition of the vanadium frit 106 containingsome of the elements listed in TABLE 3 and a β-eucryptite glass-ceramicadditive filler. In particular, the preferred vanadium frit 106 had a75:25 blend of the frit with the filler. Both these components making upthe preferred vanadium frit 106 had a mean particle size of 5 microns.TABLE 4 preferred vanadium frit 106 Sb₂O₃ 7.4 ZnO 17.6 P₂O₅ 26.5 V₂O₅46.6 TiO₂ 1.0 Al₂O₃ 1.0

TABLE 5 list a more preferred composition of the vanadium frit 106 thathas a higher amount of Sb₂O₃ and no ZnO when compared to the elementslisted in TABLE 3. TABLE 5 identifies this inventive vanadium frit 106,where all of the elements are specified in mole %: TABLE 5 morepreferred vanadium frit 106 K₂O  0-10 Fe₂O₃  0-20 Sb₂O₃  0-40 P₂O₅ 20-40V₂O₅ 30-60 TiO₂  0-20 Al₂O₃ 0-5 B₂O₃ 0-5 WO₃ 0-5 Bi₂O₃ 0-5

An exemplary blend vanadium frit 106 that contained 30% β-eucryptitefiller was made in accordance with the compositions listed in TABLE 5that had the following composition: Sb₂O₃ (23.5); P₂O₅ (27); V₂O₅(47.5); TiO₂ (1); and Al₂O₃ (1). In experiments, this exemplary blendvanadium frit 106 passed severe environmental testing (85° C./85% rhchamber) and exhibited superior aqueous durability.

It should be noted that in these experiments it was determined that theexemplary blend vanadium frit 106 had a CTE of 36.3×10⁻⁷/° C. (from roomtemperature (RT) to 250° C.) that was measured on a sample that wasfirst furnace-fired to 450° C. This CTE is close to matching the CTE of37×10⁻⁷/° C. for the substrate glass plate 102/107. In contrast, anexemplary vanadium frit 106 that did not contain the β-eucryptite fillerwas tested and had a CTE of 81.5×10⁻⁷/° C. As can be appreciated, tomatch the CTE of a glass substrate which is in the 30-40×10⁻⁷/° C.range, fillers are needed in the exemplary vanadium frit 106.

It should also be noted that most traditional low temperature sealingfrits are PbO-based, because PbO frits have good flow, and adhesionproperties. However, the exemplary blended vanadium frit 106 not onlyhas a lower CTE than PbO-based frits, but it also possess better aqueousdurability, as well being comparable to the traditional Pb-based fritswith respect to adhesion.

Moreover, it should also be noted that other stable blended vanadiumfrits 106 which had Sb₂O₃ levels as high as 28.5 have also been made andsuccessfully tested that had a composition similar to the aforementionedexemplary blend vanadium frit 106.

In addition to the aforementioned frit compositions listed in TABLES1-5, it should be understood that there may be other frit compositionswhich have yet to be developed but could be used to seal two glassplates.

Following are some of the different advantages and features of thepresent invention:

-   -   The hermetic seal 108 has the following properties:        -   Good thermal expansion match to glass substrate plates 102            and 107.        -   Low softening temperature.        -   Good chemical and water durability.        -   Good bonding to glass substrate plates 102 and 107.        -   Good bonding to copper metal leads (e.g., anode and cathode            electrodes).        -   Dense with very low porosity.        -   Pb and Cd-free.    -   It is important to understand that other types of substrate        plates 102 and 107 besides the Code 1737 glass plates and EAGLE        2000™ glass plates can be sealed to one another using the        sealing process of the present invention. For example, glass        plates 102 and 107 made by companies such as Asahi Glass Co.        (e.g., OA10 glass and OA21 glass), Nippon Electric Glass Co.,        NHTechno and Samsung Corning Precision Glass Co. can be sealed        to one another using the sealing process of the present        invention.    -   There are other considerations which should also be taken into        account in the present invention in addition to having a frit        106 made from glass that is doped with one or more transition        metals which can be melted to form a hermetic seal 108. These        considerations include having the right match between the CTEs        of the sealed glasses 102 and 107 and frit 106 and the right        match between the viscosities (e.g., strain, softening points)        of the sealed glasses 102 and 107 and frit 106. It should be        noted that residual stress measurements have indicated that it        is preferable to have the CTE of the frit 106 the same as or        lower than the CTE of the substrate glass 102 and 107. Other        considerations to achieve a “good” hermetic seal 108 include        selecting the right sealing conditions such as laser power,        focusing and velocity of sealing.    -   The OLED display 100 and method 200 offers several advantages        over the current practice in industry where an organic adhesive        is used to provide a hermetic seal in an OLED display. First,        the OLED display 100 does not require the presence of a        dessicant. Second, the rate of degradation of the traditional        UV-cured adhesive seal due to moisture is believed to be faster        than that of the inorganic seal in the OLED display 100. Third,        the proposed method 200 may substantially reduce the cycle time        (processing time) of a given component where UV-cured sealing        (organic adhesive) commonly requires a post-treatment in a        furnace for an extended time. Fourth, the OLED display 100 is        likely to be longer-lived than the traditional epoxy-sealed OLED        displays which offer poor resistance to moisture penetration.        Fifth, the OLED sealing method 200 can be easily integrated into        a manufacturing line.    -   The frits 106 of the present invention can be designed to absorb        heat in other regions besides the infrared region described        above.    -   It should be readily appreciated that in addition to the        aforementioned exemplary frits that there may be other        compositions or types of frits which exist or which have yet to        be developed but could be used in accordance with the present        invention to make a desirable OLED display.    -   The frit 106 that is pre-sealed to one of the substrate plates        102 or 107 in accordance with step 210 can be sold as a unit or        pre-sintered part to manufacturers of the OLED display 100 who        can then install the OLEDs 104 and perform the final heating and        cooling step 212 at their facility using a localized heat        source.    -   The OLED display 100 can be an active OLED display 100 or a        passive OLED display 100.    -   It should be noted that another aspect of the present invention        is to control the cooling rate of the OLED display 100 after        completing the heating step 210. Abrupt and rapid cooling may        cause large thermal strains leading to high elastic thermal        stresses on the hermetic seal 108 and the sealed plates 102 and        107. It should also be noted that the suitable cooling rate        depends on the size of the particular OLED display 100 to be        sealed and the heat dissipation rate to the environment from the        OLED display 100.

Although several embodiments of the present invention has beenillustrated in the accompanying Drawings and described in the foregoingDetailed Description, it should be understood that the invention is notlimited to the embodiments disclosed, but is capable of numerousrearrangements, modifications and substitutions without departing fromthe spirit of the invention as set forth and defined by the followingclaims.

1.-50. (canceled)
 51. A frit comprising a non-lead based glass dopedwith at least one transition metal, and a coefficient of thermalexpansion (CTE) lowering filler.
 52. The frit according to claim 51wherein the CTE lowering filler is an additive filler.
 53. The fritaccording to claim 51 wherein the CTE lowering filler is an inversionfiller.
 54. The frit according to claim 51 wherein the at least onetransition metal is selected from the group consisting of iron, copper,vanadium and neodymium.
 55. The frit according to claim 52 wherein theCTE lowering filler is a lithium alumino-silicate.
 56. The fritaccording to claim 53 wherein the CTE lowering filler is Co—Mgpyrophosphate.
 57. The frit according to claim 51 wherein the non-leadbased glass is selected from the group of glasses consisting of atitano-vanadium glass, an iron-vanadium glass, a zinc-vanadium glass, aSn—Zn-phosphate glass, a mixed alkali zinc-phosphate glass, and avanadium-phosphate glass.
 58. The frit according to claim 51 wherein thefrit comprises a coefficient of thermal expansion of about 36.3×10⁻⁷/°C. between room temperature and 250° C.
 59. The frit according to claim51 wherein the frit has a glass transition temperature T_(g) less than325° C. and a CTE less than about 130×10⁻⁷/° C. between room temperatureand 250° C.
 60. The frit according to claim 51 wherein the frit has asubstantially zero percent transmittance in the wavelength range betweenabout 800 nm and about 1500 nm.
 61. The flit according to claim 51wherein the non-lead-based glass comprises: K₂O (0-10 mole %) Fe₂O₃(0-20 mole %) Sb₂O₃ (040 mole %) P₂O₅ (2040 mole %) V₂O₅ (30-60 mole %)TiO₂ (0-20 mole %) Al₂O₃ (0-5 mole %) B₂O₃ (0-5 mole %) WO₃ (0-5 mole %)Bi₂O₃ (0-5 mole %)
 62. The frit according to claim 51 wherein thenon-lead-based glass comprises: K₂O (0-10 mole %) Fe₂O₃ (0-20 mole %)Sb₂O₃ (0-20 mole %) ZnO (0-20 mole %) P₂O₅ (20-40 mole %) V₂O₅ (30-60mole %) TiO₂ (0-20 mole %) Al₂O₃ (0-5 mole %) B₂O₃ (0-5 mole %) WO₃ (0-5mole %) Bi₂O₃ (0-5 mole %)
 63. The frit according to claim 51 whereinthe non-lead-based glass consists essentially of: Sb₂O₃ (7.4 mole %) ZnO(17.6 mole %) P₂O₅ (16.5 mole %) V₂O₅ (46.6 mole %) TiO₂ (1.0 mole %)Al₂O₃ (1.0 mole %)
 64. The frit according to claim 51 which, whendisposed between first and second glass substrates and irradiatedthrough one or more of the substrates by an irradiation source having awavelength between about 800 nm and 2000 nm, absorbs more light from theirradiation source when compared to light absorbed by the substrates.65. The frit according to claim 64 wherein the frit is melted and formsa hermetic seal between the first and second substrates.
 66. A fritcomprising one or more radiation absorbing ions, a substantially zerotransmittance in the wavelength range between about 800 nm and 10.6 μm,and a coefficient of thermal expansion (CTE) less than about 130×10⁻⁷/°C. between room temperature and 250° C.
 67. The frit according to claim66 wherein the one or more radiation absorbing ions are ions of atransition metal.
 68. The frit according to claim 67 wherein thetransition metal is selected from the group consisting of iron, copper,vanadium and neodymium.
 69. The frit according to claim 66 wherein thefrit further comprises a coefficient of thermal expansion (CTE) loweringfiller.
 70. The frit according to claim 69 wherein the CTE loweringfiller is an additive filler.
 71. The frit according to claim 69 whereinthe filler is an inversion filler.
 72. The frit according to claim 69wherein the filler is a lithium alumino-silicate.
 73. The frit accordingto claim 69 wherein the CTE lowering filler is β-eucryptite.
 74. Thefrit according to claim 69 wherein the filler is Co—Mg pyrophosphate.75. A frit comprising a coefficient of thermal expansion (CTE) loweringfiller and a glass comprising: K₂O (0-10 mole %) Fe₂O₃ (0-20 mole %)Sb₂O₃ (0-40 mole %) P₂O₅ (20-40 mole %) V₂O₅ (30-60 mole %) TiO₂ (0-20mole %) Al₂O₃ (0-5 mole %) B₂O₃ (0-5 mole %) WO₃ (0-5 mole %) Bi₂O₃ (0-5mole %)
 76. The frit according to claim 75 wherein the CTE loweringfiller is an additive filler.
 77. The frit according to claim 75 whereinthe CTE lowering filler is an inversion filler.
 78. The frit accordingto claim 75 wherein the filler is a lithium alumino-silicate.
 79. Thefrit according to claim 75 wherein the filler is Co—Mg pyrophosphate.80. The frit according to claim 75 wherein the CTE of the frit is lessthan about 130×10⁻⁷/° C. between room temperature and 250° C.
 81. Thefrit according to claim 75 wherein a glass transition temperature T_(g)of the frit is less than about 325° C.
 82. A frit comprising acoefficient of thermal expansion (CTE) lowering filler and a glasscomprising: K₂O (0-10 mole %) Fe₂O₃ (0-20 mole %) Sb₂O₃ (0-20 mole %)ZnO (0-20 mole %) P₂O₅ (20-40 mole %) V₂O₅ (30-60 mole %) TiO₂ (0-20mole %) Al₂O₃ (0-5 mole %) B₂O₃ (0-5 mole %) WO₃ (0-5 mole %) Bi₂O₃ (0-5mole %)
 83. The frit according to claim 82 wherein the CTE loweringfiller is an additive filler.
 84. The frit according to claim 82 whereinthe CTE lowering filler is an inversion filler.
 85. The frit accordingto claim 82 wherein the filler is a lithium alumino-silicate.
 86. Thefrit according to claim 82 wherein the filler is Co—Mg pyrophosphate.87. The frit according to claim 82 wherein the CTE of the frit is lessthan about 130×10⁻⁷/° C. between room temperature and 250° C.
 88. Thefrit according to claim 80 wherein a glass transition temperature T_(g)of the frit is less than about 325° C.
 89. A frit comprising acoefficient of thermal expansion (CTE) lowering filler and a glassconsisting essentially of: Sb₂O₃ (7.4 mole %) ZnO (17.6 mole %) P₂O₅(16.5 mole %) V₂O₅ (46.6 mole %) TiO₂ (1.0 mole %) Al₂O₃ (1.0 mole %)90. The frit according to claim 89 wherein a ratio of glass to filler is75%:25%.
 91. A frit comprising a coefficient of thermal expansion (CTE)lowering filler and a glass comprising at least one transition metalselected from the group of glasses consisting of a titano-vanadiumglass, an iron-vanadium glass, a zinc-vanadium glass, a Sn—Zn-phosphateglass, a mixed alkali zinc-phosphate glass, a vanadium-phosphate glass,a Pb-borate glass, and a mixed alkali zinc-phosphate glass with vanadiumand lead, and wherein the frit has a coefficient of thermal expansion(CTE) less than about 140×10⁻⁷/° C. between about room temperature and250° C., and a glass transition temperature T_(g) less than about 350°C.
 92. The frit according to claim 91 wherein the CTE lowering filler isan additive filler.
 93. The frit according to claim 91 wherein the CTElowering filler is an inversion filler.
 94. The frit according to claim91 wherein the CTE lowering filler is a lithium alumino-silicate. 95.The frit according to claim 91 wherein the CTE lowering filler is Co—Mgpyrophosphate.
 96. The frit according to claim 91 wherein the glasscomprises: K₂O (0-10 mole %) Fe₂O₃ (0-20 mole %) Sb₂O₃ (0-40 mole %)P₂O₅ (20-40 mole %) V₂O₅ (30-60 mole %) TiO₂ (0-20 mole %) Al₂O₃ (0-5mole %) B₂O₃ (0-5 mole %) WO₃ (0-5 mole %) Bi₂O₃ (0-5 mole %)
 97. Thefrit according to claim 96 wherein the ratio of glass to filler is70%:30%.
 98. The frit according to claim 91 wherein the glass comprises:K₂O (0-10 mole %) Fe₂O₃ (0-20 mole %) Sb₂O₃ (0-20 mole %) ZnO (0-20 mole%) P₂O₅ (20-40 mole %) V₂O₅ (30-60 mole %) TiO₂ (0-20 mole %) Al₂O₃ (0-5mole %) B₂O₃ (0-5 mole %) WO₃ (0-5 mole %) Bi₂O₃ (0-5 mole %)
 99. Thefrit according to claim 91 which, when disposed between first and secondglass substrates and irradiated through one or more of the substrates byan irradiation source having a wavelength between about 800 nm and 2000μm, melts and forms a hermetic seal between the substrates.
 100. Thefrit according to claim 91 wherein the frit is free of cadmium.